95 Maxima Smog Failure High NO
01-14-2015, 01:08 PM
#1
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95 Maxima Smog Failure High NO
Need your help guys. I need to get my car registered and just failed smog for high NO. However, it barely fails. The readings are:
Fails - 510 at 15 mph. Max is 495
Pass - 482 at 25 mph. Max is 492
I already cleaned everything including the throttle body, EGR tube, and intake manifold. All plugs have been replaced.
The problem, I think, is that the EGR is not opening. Per the FSM, the EGR should open between 2K-4K RPMs. It's not doing anything. I did test the EGR and the diaphragm is good. The EGR valve lifts and holds a vacuum. It also works when I directly connect the EGR to the throttle body vacuum port. I've changed all the vacuum hoses.
I've also check the EGR solenoid. With the car on, the solenoid connector reads 12.5v and I can actuate the solenoid manually with external voltage.
The smog guy says it's probably the EGRC-BPT valve. The FSM doesn't show much other than a quick vacuum test. Are there any other tests I can do to this BPT valve?
What else could prevent this damn piece of ****e EGR system from getting a vacuum?
Fails - 510 at 15 mph. Max is 495
Pass - 482 at 25 mph. Max is 492
I already cleaned everything including the throttle body, EGR tube, and intake manifold. All plugs have been replaced.
The problem, I think, is that the EGR is not opening. Per the FSM, the EGR should open between 2K-4K RPMs. It's not doing anything. I did test the EGR and the diaphragm is good. The EGR valve lifts and holds a vacuum. It also works when I directly connect the EGR to the throttle body vacuum port. I've changed all the vacuum hoses.
I've also check the EGR solenoid. With the car on, the solenoid connector reads 12.5v and I can actuate the solenoid manually with external voltage.
The smog guy says it's probably the EGRC-BPT valve. The FSM doesn't show much other than a quick vacuum test. Are there any other tests I can do to this BPT valve?
What else could prevent this damn piece of ****e EGR system from getting a vacuum?
01-25-2015, 10:51 AM
#2
I have a similar problem as you. I failed the Nox emissions by 3 times the limit. Tested the EGR, and the diaphragm was working and holding vacuumn. Also, tested the EGRC solenoid harness for power, and the solenoid itself to see if operational. Everything checked out fine.
When I revved the engine, the diaphragm did nothing. Took out the line from the EGR and blipped the throttle and felt no vacuumn of any kind.
Looked around, then noticed that the wide open/closed throttle switch harness (next to the TPS) was frayed and I could see exposed wiring. So I spliced and replaced the grey harness and retested.
I have not taken it to emissions to actually verify the reduction in nox, but when I revved/blipped the engine, I could feel the diaphragm moving. I took out the line and blipped the engine and felt unmistakable vacuumn.
I'm not sure how the wide open/closed throttle switch could have played a role in the EGR not getting the proper vacuumn...could just be coincidence?
When I revved the engine, the diaphragm did nothing. Took out the line from the EGR and blipped the throttle and felt no vacuumn of any kind.
Looked around, then noticed that the wide open/closed throttle switch harness (next to the TPS) was frayed and I could see exposed wiring. So I spliced and replaced the grey harness and retested.
I have not taken it to emissions to actually verify the reduction in nox, but when I revved/blipped the engine, I could feel the diaphragm moving. I took out the line and blipped the engine and felt unmistakable vacuumn.
I'm not sure how the wide open/closed throttle switch could have played a role in the EGR not getting the proper vacuumn...could just be coincidence?
Last edited by RIPTIDER; 01-25-2015 at 10:55 AM.
01-25-2015, 03:57 PM
#3
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Wide open throttle switch isn't going to effect EGR, it's signal is used by the transmission to shift at full line pressure and also disengages the a/c compressor.
EGR actuation is engine temperature related, it doesn't operate until it's up to operating temp.
EGR actuation is engine temperature related, it doesn't operate until it's up to operating temp.
01-25-2015, 08:16 PM
#4
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I have a similar problem as you. I failed the Nox emissions by 3 times the limit. Tested the EGR, and the diaphragm was working and holding vacuumn. Also, tested the EGRC solenoid harness for power, and the solenoid itself to see if operational. Everything checked out fine.
When I revved the engine, the diaphragm did nothing. Took out the line from the EGR and blipped the throttle and felt no vacuumn of any kind.
Looked around, then noticed that the wide open/closed throttle switch harness (next to the TPS) was frayed and I could see exposed wiring. So I spliced and replaced the grey harness and retested.
I have not taken it to emissions to actually verify the reduction in nox, but when I revved/blipped the engine, I could feel the diaphragm moving. I took out the line and blipped the engine and felt unmistakable vacuumn.
I'm not sure how the wide open/closed throttle switch could have played a role in the EGR not getting the proper vacuumn...could just be coincidence?
When I revved the engine, the diaphragm did nothing. Took out the line from the EGR and blipped the throttle and felt no vacuumn of any kind.
Looked around, then noticed that the wide open/closed throttle switch harness (next to the TPS) was frayed and I could see exposed wiring. So I spliced and replaced the grey harness and retested.
I have not taken it to emissions to actually verify the reduction in nox, but when I revved/blipped the engine, I could feel the diaphragm moving. I took out the line and blipped the engine and felt unmistakable vacuumn.
I'm not sure how the wide open/closed throttle switch could have played a role in the EGR not getting the proper vacuumn...could just be coincidence?
01-27-2015, 06:35 PM
#5
As per The Wizard's reply in previous thread:
My readings aren't even close compared to yours, so these tricks should do it. I was thinking to do the same, if I came as close to passing, as your car came. The only thing holding me back is that its snowing where I live, and water + wetter wouldn't be a good idea now. 100 octane at select Sunoco locations wouldn't hurt either.
I would then just flush out the coolant system, since it's due for one, and refill with preferred coolant, and done.
That's correct. EGR is the biggest culprit for high NOx readings.
Also, don't go for a spirited drive before the test. You want the exact opposite. Any good tech knows to let the car cool down for hours, then start it and run the test quickly. The spirited driving technique is good for keeping the other gas levels down.
Unfortunately, there is no easy fix for this. You'll have to spend the time to clean the EGR system or pay someone to do an upper cylinder head cleaning to remove carbon deposits and lower the compression. However, there are a few little tricks you can do to help your cause. Have your cooling system be nothing but water and a full bottle of water wetter. Also, use the highest octane gas you can find, even race gas. These two tips are relatively cheap and easy and will keep the cylinder heads temps down which in turn will lower your Nox readings.
Also, don't go for a spirited drive before the test. You want the exact opposite. Any good tech knows to let the car cool down for hours, then start it and run the test quickly. The spirited driving technique is good for keeping the other gas levels down.
Unfortunately, there is no easy fix for this. You'll have to spend the time to clean the EGR system or pay someone to do an upper cylinder head cleaning to remove carbon deposits and lower the compression. However, there are a few little tricks you can do to help your cause. Have your cooling system be nothing but water and a full bottle of water wetter. Also, use the highest octane gas you can find, even race gas. These two tips are relatively cheap and easy and will keep the cylinder heads temps down which in turn will lower your Nox readings.
My readings aren't even close compared to yours, so these tricks should do it. I was thinking to do the same, if I came as close to passing, as your car came. The only thing holding me back is that its snowing where I live, and water + wetter wouldn't be a good idea now. 100 octane at select Sunoco locations wouldn't hurt either.
I would then just flush out the coolant system, since it's due for one, and refill with preferred coolant, and done.
Last edited by RIPTIDER; 01-27-2015 at 07:18 PM.
01-27-2015, 07:06 PM
#6
The car was at operating temps. The only thing different I did was, when I didn't feel any vacuum, I disconnected the t-connection coming from the throttle to the EGR or solenoid. The previous manifold was a MEVI, that was installed by an ex-friend, and I don't recall where that vacuum line connected. When I installed the USIM, I just taped the extra line from the tapped T-connection closed. Maybe that was the cause in loss of vacuum? Or, it could be as simple as manually testing the EGR diaphragm by pressing up on it, or the hand held vacuum test that freed up some charcoal bit pieces?
Anyways, the throttle switch had to be replaced. I'm thinking to go tomorrow and test it to see what my readings are again, and spend another emissions fee. Otherwise, I will have to take apart and inspect the EGR, EGRC-BPT valve, and test the ECT sensor. I'm lazy!
Don't mean to hijack the thread, but these problematic symptoms are similar. Plus, it looks like SupaMaxima and I are going to perform the same troubleshooting process together.
Last edited by RIPTIDER; 01-27-2015 at 07:21 PM.
01-27-2015, 09:10 PM
#7
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Thread Starter
Join Date: Dec 2000
Posts: 217
The car was at operating temps. The only thing different I did was, when I didn't feel any vacuum, I disconnected the t-connection coming from the throttle to the EGR or solenoid. The previous manifold was a MEVI, that was installed by an ex-friend, and I don't recall where that vacuum line connected. When I installed the USIM, I just taped the extra line from the tapped T-connection closed. Maybe that was the cause in loss of vacuum? Or, it could be as simple as manually testing the EGR diaphragm by pressing up on it, or the hand held vacuum test that freed up some charcoal bit pieces?
Anyways, the throttle switch had to be replaced. I'm thinking to go tomorrow and test it to see what my readings are again, and spend another emissions fee. Otherwise, I will have to take apart and inspect the EGR, EGRC-BPT valve, and test the ECT sensor. I'm lazy!
Don't mean to hijack the thread, but these problematic symptoms are similar. Plus, it looks like SupaMaxima and I are going to perform the same troubleshooting process together.
Anyways, the throttle switch had to be replaced. I'm thinking to go tomorrow and test it to see what my readings are again, and spend another emissions fee. Otherwise, I will have to take apart and inspect the EGR, EGRC-BPT valve, and test the ECT sensor. I'm lazy!
Don't mean to hijack the thread, but these problematic symptoms are similar. Plus, it looks like SupaMaxima and I are going to perform the same troubleshooting process together.
01-28-2015, 06:19 AM
#8
I did test the EGR and the diaphragm is good. The EGR valve lifts and holds a vacuum. It also works when I directly connect the EGR to the throttle body vacuum port.
I've also check the EGR solenoid. With the car on, the solenoid connector reads 12.5v and I can actuate the solenoid manually with external voltage.
I've also check the EGR solenoid. With the car on, the solenoid connector reads 12.5v and I can actuate the solenoid manually with external voltage.
The result you want is at 4:47 here.
01-28-2015, 08:52 AM
#9
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Posts: 217
01-31-2015, 02:28 PM
#10
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Join Date: Sep 2001
Posts: 182
I had the same problem. I tested everything and they were working. My problem was the fuel pump. What people don't realize is that Maxima's emission system works with back pressure from the exhaust. So if your fuel pressure is low, your back pressure will be low. Egr system will not work properly. My fuel pressure was off by 3-4 psi.
02-05-2015, 07:52 PM
#12
SupaMaxima, how is the troubleshooting going?
I failed the emissions again.
When I disconnected the T-connection, I mistakenly attached an extra one way valve from the right side throttle body to vacuum gallery A. I'm assuming this gave me the extra "unmistakable vacuum" I felt going to the EGR, when I felt it lifting. I then restarted the car, and immediately received a MAP/BARO switch code P1105. No vacuum going to the MAP/BARO solenoid, nor the Absolute pressure sensor. I tested both solenoid and sensor, and everything checked out. Finally, took out the one way valve and unmistakable vacuum was restored to the MAP/BARO switch and Absolute pressure sensor. But again, there was weak vacuum going to the EGR valve itself. It barley lifted up, when blipping the throttle, between 2-4k RPMs fully warmed up. Already tested the EGRC solenoid and EGR valve and both operate within FSM specifications.
Started tracing where the vacuum begins, and where it starts to die off. I get powerful vacuum from the throttle body to the EGRC solenoid valve. Also on the way from the EGRC solenoid to the EGR gallery A, then it just gets weak vacuum to the EGR valve itself.
I have narrowed it down to an intermittent issue with the EGRC solenoid, the pipe coming from the EGR to the EGRC BPT ( 14751 being clogged or cracked somehow), or a faulty EGRC BPT valve. Also, is the 14755 rubber hose that connects to the 14751 metal tube some kind of OEM part? I thought that since the rubber tube was receiving hot re-circulated exhaust from the EGR that it would melt? But, I have taken off 3 EGRC-BPT valves from other Maximas, and they seem to have only a standard vacuum line, including mine that had zip ties on it from who knows?
I will recheck everything, but if all else comes to worse, I will just connect a y-type vacuum connection line from where I get the most vacuum (throttle body to the EGRC solenoid valve), then another y-type vacuum connection from the EGRC BPT valve to the EGR, and bypass the vacuum issue entirely. I have spent way too long on this, and throwing NEW parts at this car is a luxury I can consider in the future, AFTER I pass my emissions.
SupaMaxima, chime in on this so we can get this wrapped up together.
I failed the emissions again.
When I disconnected the T-connection, I mistakenly attached an extra one way valve from the right side throttle body to vacuum gallery A. I'm assuming this gave me the extra "unmistakable vacuum" I felt going to the EGR, when I felt it lifting. I then restarted the car, and immediately received a MAP/BARO switch code P1105. No vacuum going to the MAP/BARO solenoid, nor the Absolute pressure sensor. I tested both solenoid and sensor, and everything checked out. Finally, took out the one way valve and unmistakable vacuum was restored to the MAP/BARO switch and Absolute pressure sensor. But again, there was weak vacuum going to the EGR valve itself. It barley lifted up, when blipping the throttle, between 2-4k RPMs fully warmed up. Already tested the EGRC solenoid and EGR valve and both operate within FSM specifications.
Started tracing where the vacuum begins, and where it starts to die off. I get powerful vacuum from the throttle body to the EGRC solenoid valve. Also on the way from the EGRC solenoid to the EGR gallery A, then it just gets weak vacuum to the EGR valve itself.
I have narrowed it down to an intermittent issue with the EGRC solenoid, the pipe coming from the EGR to the EGRC BPT ( 14751 being clogged or cracked somehow), or a faulty EGRC BPT valve. Also, is the 14755 rubber hose that connects to the 14751 metal tube some kind of OEM part? I thought that since the rubber tube was receiving hot re-circulated exhaust from the EGR that it would melt? But, I have taken off 3 EGRC-BPT valves from other Maximas, and they seem to have only a standard vacuum line, including mine that had zip ties on it from who knows?
I will recheck everything, but if all else comes to worse, I will just connect a y-type vacuum connection line from where I get the most vacuum (throttle body to the EGRC solenoid valve), then another y-type vacuum connection from the EGRC BPT valve to the EGR, and bypass the vacuum issue entirely. I have spent way too long on this, and throwing NEW parts at this car is a luxury I can consider in the future, AFTER I pass my emissions.
SupaMaxima, chime in on this so we can get this wrapped up together.
02-11-2015, 02:23 PM
#14
Used a Y connection from the vacuumn gallery to EGRC solenoid, then another Y connection at the EGR-BPT going to the EGR and now the EGR lifts and passes the NO test on the emissions! Unfortunately, for some reason, now I am failing HC by a lot. I wonder if it's directly due to the fact I used additional vacuumn to get the EGR to operate? Never had an issue with unburnt fuel before. Always have passesd the HC portion of the emissions test.
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